We are examining the adaptation of synaptic events to changing neural inputs and relate this to the adaptation of the whole organism to changing internal and external environments. The synapses on which we are focusing are those which utilize biogenic amines (including muscarinic, cholinergic synapses). We believe these synapses play a unique, modulatory role in neural processing, a contrasted with the rapid, primary events mediated by the amino acids and acetylcholine (nicotinic). During the current year we are focusing on studies relating stress to brain catecholamines. First we are examining the acute effects of stressors on catecholamine metabolism in different brain regions. Our measures include catecholamine content, metabolite levels, and tyrosine hydroxylase activity (TH). We are also examining the postsynaptic effects of stress-induced catecholamine release, including changes in cAMP content and in carbohydrate metabolism. Finally, we are beginning to examine the chronic effects of stress on catecholamine synthesis. In addition to these studies we are continuing our interest in synthesis-secretion coupling in monoamine-containing nerve terminals. Our overall effort can be viewed at several different levels. First, we are examining the role of these transmitters in the behavioral responses to severe regulatory imbalance. Second, we are using such stresses to alter impulse flow in neural systems to examine the ability of these systems to adapt to changing demands. Thus, we anticipate that our results will provide basic biochemical dat, information about the functional significance of these transmitters, and insights into plasticity at the synaptic level.